JP2010513600A - Polyethylene-syndiotactic polypropylene compositions and their processing - Google Patents

Abstract

A moldable polypropylene composition comprising a mixture of a large amount of syndiotactic polypropylene and a small amount of polyethylene wax. This syndiotactic polypropylene has a nominal recrystallization temperature, an original small melting peak and a high original melting peak. Polyethylene wax provides a recrystallization temperature for the mixture that is higher than the recrystallization temperature of syndiotactic polypropylene alone, and between the original small melting peak and the original large melting peak of syndiotactic polypropylene alone. Resulting in a small and large melting peak of the mixture having a temperature difference less than the difference between A method for producing a polypropylene product, wherein the polyethylene-syndiotactic polypropylene composition described above is used and heated to obtain a plastic object of syndiotactic polypropylene and polyethylene, which is then processed to obtain a product.
[Selection] Figure 1

Description

  The present invention relates to syndiotactic polypropylene incorporating a small amount of polyethylene wax, and a method of processing such polypropylene to produce a polypropylene product.

  Stereoregular polypropylene in the form of propylene homopolymers or propylene copolymers incorporating small amounts of other alpha olefins such as ethylene or butylene as comonomers can be processed to form products such as films, fibers, and molded products. . Of the stereoregular polypropylene, perhaps isotactic polypropylene is most widely used. For example, isotactic polypropylene can be used in the production of relatively thin films that are biaxially oriented by heating the polypropylene and then extruding with a slot die and stretching the film in both the longitudinal and transverse directions. is there. Isotactic polypropylene can be extruded from small orifices to produce fibers, or blow molded to produce molded products such as containers and tightly shaped articles, or in compression molds Can be injected.

  The structure of isotactic polypropylene is characterized by methyl groups attached to the tertiary carbon atoms of successive propylene monomer units attached to the same side of the polymer backbone. That is, all the methyl groups are above or below the polymer chain. Isotactic polypropylene has the chemical formula

により図示可能である。アイソタクチックおよびシンジオタクチックポリプロピレンなどの立体規則性ポリマーは、フィッシャー投影式の形で特徴付け可能である。フィッシャー投影式を用いれば、式（１）により示されるアイソタクチックポリプロピレンの立体化学的シーケンスは

Can be illustrated. Stereoregular polymers such as isotactic and syndiotactic polypropylene can be characterized in a Fischer projection form. Using the Fischer projection formula, the stereochemical sequence of isotactic polypropylene represented by formula (1) is

のように特徴付け可能である。構造を記述するもう一つの方法はＮＭＲの使用によるものである。アイソタクチックペンタッドのボーベイのＮＭＲ命名法は．．．ｍｍｍｍ．．．であり、各「ｍ」は「メソ」ダイアッドまたはポリマー鎖の平面の同一の側上の連続的なメチル基を表す。当業界で既知であるように、鎖構造中のいかなる偏差（ｄｅｖｉａｔｉｏｎ）または反転も、アイソタクティシティ度とポリマーの結晶性を低下させる。

It can be characterized as follows. Another way of describing the structure is by using NMR. The NMR nomenclature for the isotactic pentad Bovey is: . . mmmm. . . Where each “m” represents a “meso” dyad or successive methyl groups on the same side of the plane of the polymer chain. As is known in the art, any deviation or inversion in the chain structure reduces the degree of isotacticity and the crystallinity of the polymer.

  In contrast to the isotactic structure, syndiotactic propylene polymers are those in which methyl groups attached to the tertiary carbon atoms of successive monomer units in the polymer chain are attached to alternating sides of the polymer plane. Using the Fischer projection formula, the structure of syndiotactic polypropylene is

のように表示可能である。シンジオタクティシティは、シンジオタクチックダイアッドおよびペンタッドｒｒｒｒ（ここで、各「ｒ」はラセミダイアッドを表す）の形で特徴付け可能である。シンジオタクチックポリマーは半結晶性であり、アイソタクチックポリマーに類似して、キシレンに本質的に不溶性である。この結晶性は、非結晶性であり、キシレンに高可溶性であるアタクチックポリマーからシンジオタクチックおよびアイソタクチックポリマーを区別する。アタクチックポリマーは、ポリマー鎖中の繰り返し単位立体配置の規則的な順序を示さず、本質的にワックス状製品を形成する。

Can be displayed. Syndiotacticity can be characterized in the form of syndiotactic dyads and pentads rrrr (where each “r” represents a racemic dyad). Syndiotactic polymers are semicrystalline and, like isotactic polymers, are essentially insoluble in xylene. This crystallinity distinguishes syndiotactic and isotactic polymers from atactic polymers that are non-crystalline and highly soluble in xylene. Atactic polymers do not exhibit a regular order of repeat unit configurations in the polymer chain and essentially form a waxy product.

  In accordance with the present invention, there is provided a processable polypropylene composition comprising a mixture of syndiotactic polypropylene as a major component and polyethylene wax as a relatively minor component. This syndiotactic polypropylene is characterized by a designated recrystallization temperature, an original minor melting peak, and an original major melting peak that is found at a temperature higher than the original minor melting peak. The polyethylene wax is present in the blend with the syndiotactic polypropylene in an amount that provides a recrystallization temperature for the blend that is higher than the recrystallization temperature of the syndiotactic polypropylene alone. This polyethylene wax also results in the minor and major melting peaks of the mixture having a temperature difference that is less than the difference between the original minor melting peak and the original major melting peak of syndiotactic polypropylene alone. In one embodiment, the temperature difference between the minor and major melting peaks of the blend incorporating the polyethylene wax is the temperature between the original minor and major melting peaks without the addition of the polyethylene wax. Decreases in at least 2 ° C increments than the difference. In one embodiment, the polyethylene wax has a molecular weight less than that of syndiotactic polypropylene and is at least 5% higher than the recrystallization temperature of the syndiotactic polypropylene alone, the recrystallization temperature of the formulation. It is present in an amount that causes an increase.

  The moldable polypropylene composition of the present invention is also characterized by the slope of the curve defined by the original minor melting peak of syndiotactic polypropylene alone and the minor melting peak of the blend of polyethylene wax and syndiotactic polypropylene. Attached. This slope is greater than the slope of the curve defined by the original major melting peak of syndiotactic polypropylene and the major melting peak of the blend of syndiotactic polypropylene and polyethylene wax.

  In one embodiment of the present invention, the moldable composition is recrystallized from the mixture at least 1 ° C. lower than the difference between the original recrystallization temperature and the original minor melting peak. Characterized in the form of a temperature difference between the temperature and the minor melting peak of this mixture. In another embodiment, the polyethylene wax comprises: At least to provide an amount in the range of 1-10% by weight. It is present in this blend in an amount ranging from 1% by weight up to 10% by weight.

  In another aspect of the invention, a method is provided for producing a polypropylene product using the polyethylene-syndiotactic polypropylene composition described above. The polyethylene-syndiotactic polypropylene composition is heated to a temperature above the major melting peak of the composition to obtain a syndiotactic polypropylene plastic body incorporating a small amount of polyethylene. The plastic body is processed into the desired shape to obtain a product preform and then cooled to a temperature below the recrystallization temperature of the blend to obtain the product. This plastic body can be processed by being extruded from a slot die system to obtain a polypropylene film. In another embodiment of the invention, the plastic article can be blow molded or introduced into a closed mold and then cooled to a temperature below the recrystallization temperature to produce a molded product, or plastic An object can be extruded from a fiber die orifice to produce a long fiber preform. The preform is then cooled to a temperature below the recrystallization temperature and then stressed by stretching to form the final fiber product.

FIG. 1 is a graphical representation of increasing recrystallization temperature as a function of polyethylene wax concentration in syndiotactic polypropylene and decreasing incremental difference between minor and major melting peaks. FIG. 2 is a graphical representation of major and minor melting peaks as a function of polyethylene wax concentration in a syndiotactic polypropylene mixture.

The syndiotactic polypropylene used in the practice of the present invention can be characterized by microcrystalline properties and fluidity forms that are important in the processability of polymer products. The microstructure and flowable product of syndiotactic polypropylene is described in US Pat. No. 6,184,326 to Razavi et al. As disclosed therein, Rasemidai syndiotactic polypropylene, and molecular weight, is defined by the ratio of weight average molecular weight M _w of to the number average molecular weight M _n, and molecular weight distribution M _{w /} M _n, as indicated by r It can be characterized in the form of a microstructure in the form of a percentage of the racemic triad indicated by ADD, racemic triad indicated by rr, and racemic pentad indicated by rrrr. Peaks characterized by polymerizing propylene to form a lower melting point identified as Tm1 in the Razavi patent and a higher melting point identified as Tm2 as further described in the patent to Razavi et al. Temperature syndiotactic polypropylene can be produced. For a further description of syndiotactic polypropylene and its microstructure, flow properties, and melting point properties, see the aforementioned US Pat. No. 6,184,326, incorporated herein by reference. .

  The syndiotactic polypropylene used in the present invention may have a relatively high syndiotacticity as measured by the percentage of racemic pentad of the syndiotactic polypropylene. In one embodiment, the microstructure is characterized by at least 70% racemic pentad, more particularly at least 75% racemic pentad, and even at least 80% racemic pentad. The molecular weight of the syndiotactic polypropylene used in the present invention can be any suitable value, but is typically substantially higher than the polyethylene wax mixed with the syndiotactic polypropylene. This molecular weight distribution can be broad or narrow depending on the end use of the polymer. This molecular weight distribution depends on the choice of the particular transition metal used in the syndiospecific catalyst as disclosed in US Pat. No. 6,184,326 to Razavi et al. Mentioned above, or two different syndiospecificities. It can be controlled by using metallocene.

  The polyethylene wax incorporated into the syndiotactic polypropylene is usually present in an amount of at least 0.1% by weight or in an amount of at least 1% by weight. The polyethylene wax concentration can vary up to a value of about 10% by weight of syndiotactic polypropylene, but is usually used in slightly lesser amounts of about 1% by weight. As described above, as shown by the following experiment, the amount of syndiotactic polypropylene can be varied to obtain the desired flow characteristics of the syndiotactic polypropylene-polyethylene wax mixture. The aforementioned polyethylene wax usually has a molecular weight substantially lower than the molecular weight of syndiotactic polypropylene. Usually, the molecular weight of polyethylene wax is 5,000 or less. Usually, this molecular weight varies within the range of 1,000-3,000.

  In processing a syndiotactic polypropylene-polyethylene wax mixture, the solid polymer product, when gradually heated, reaches a first low temperature melting peak, characterized in this specification as a minor melting peak, and further heating. This leads to a second hot melting peak characterized as a major melting peak. The molten polymer product then reaches a recrystallization peak that is significantly lower than the temperature of the minor melting peak as it cools. In the present invention, the minor and major melting peaks are brought closer to each other than is observed for pure syndiotactic polypropylene, and the recrystallization peak is either original syndiotactic polypropylene or pure. The processing of the syndiotactic polypropylene-polyethylene wax mixture can also be controlled and enhanced by increasing to a value greater than that observed for syndiotactic polypropylene, i.e., polypropylene without polyethylene wax.

  In experiments related to the present invention, four samples of syndiotactic polypropylene were tested for minor and major melting peaks and flow characteristics characterized by recrystallization temperature. Three samples incorporated various concentrations of polyethylene wax, and one sample consisted only of syndiotactic polypropylene with no polyethylene wax added.

  The syndiotactic polypropylene used in this experiment was highly crystalline with> 90% syndiotactic dyad and> 75% syndiotactic pentad. This syndiotactic polypropylene was produced by polymerization with a syndiospecific metallocene of the type disclosed in the aforementioned US Pat. No. 6,184,326. This polymer had a weight average molecular weight of about 170,000 and a number average molecular weight of about 35,000, resulting in a molecular weight distribution of 4.8.

  The polyethylene wax used at various concentrations in admixture with syndiotactic polypropylene had a molecular weight of about 3,000 and a melting temperature of about 128 ° C. The polyethylene wax was used in a composition that varied from 0.1 wt% polyethylene wax to 5.0 wt% polyethylene wax. The percentage of polyethylene wax is determined on the basis of a mixture of polyethylene and syndiotactic polypropylene. Thus, a formulation containing 5.0 wt% polyethylene incorporated 5 parts by weight polyethylene and 95 parts by weight syndiotactic polypropylene.

  The polyethylene wax used was used in two forms. One was a micronized form with an average particle size of 7 microns and the other was in the form of a pills of particles with an average of 200 microns. Pure syndiotactic polypropylene and polyethylene-syndiotactic polypropylene blends were molded into plaques having a thickness of 0.05 ". The properties of the blends and plaques so formed are shown in Table I. The four samples used in Table I are those identified as Samples 1, 2, 3, and 4, and Sample 1 is pure polypropylene, column 1 indicates the concentration of polyethylene wax. Column 2 shows the properties of the wax used in the sample of interest, Column 3 shows the haze of 0.05 inch plaques, and the haze ratio was determined according to ASTM method D1003 (Procedure A). The fourth column shows the relative injection speed in the molding of the plaque, the fifth column shows the cooling time of the plaque in seconds, and the sixth column during the entire plaque manufacturing cycle. It is shown in seconds.

Table II represents the flow characteristics of the four samples shown in Table I. Table II shows the recrystallization temperature T _r and the major temperature peak T ₁ and minor temperature peak T ₂ in ° C in the first three columns of the data. The fourth column shows the difference between the major melting peak (T ₁ ) and the minor melting peak (T ₂ ) for each of samples 1, 2, 3, and 4. The fifth column indicates the difference between T ₂ and T _r, the last column indicates the difference between T ₁ and T _r.

A portion of the data shown in Table II is displayed graphically in FIGS. Curve 2 in FIG. 1 is a plot of the incremental difference D at 0 ° C. between the major and minor melting peaks plotted on the vertical axis against the polyethylene concentration P plotted on the horizontal axis (T ₁ -T ₂ ). 3 is a graph of the increase in the value of T _r recrystallization temperature IT _r plotted on the ordinate vs. the polyethylene concentration, P with respect to the sample 1.

Figure 2 in the curve 4 is a plot of the major melting peak T _1, plotted on the ordinate vs. the polyethylene concentration, P, plotted on the horizontal axis. Curve 6 is a plot of the minor melting peak T _2, plotted on the ordinate vs. the polyethylene concentration, P, plotted on the horizontal axis. Examining the experiments, it appears that the initial slight decrease in T ₁ and T ₂ can be anomalous data resulting from experimental errors, and thus syndicate containing syndiotactic polypropylene alone and 0.1 wt% polyethylene. For tactic polypropylene, curves 4 and 6 in the graph are drawn through the average of the data.

  As can be seen from the experimental studies referenced above, the addition of polyethylene wax, even in small amounts, enhances the processability of syndiotactic polypropylene during the formation of the initial preform and the production and processing of the desired product. Produces some beneficial results of shape. A significant increase in recrystallization temperature is observed with an increase in the minor melting peak. The major melting peak is more or less flat when the polyethylene concentration is increased, and the two melting peaks tend to coalesce and syndiotactic polypropylene processability is enhanced during preform formation. Using at least 1% by weight of polyethylene wax, a significant increase in recrystallization peak can be achieved in conjunction with substantial fusion of the major and minor melting peaks. As shown by the data shown in FIG. 1, where curves 2 and 3 reach an intersection near 2% by weight, a mixture is obtained at or above this intersection using at least 2% by weight polyethylene wax.

  As shown by the data in FIG. 2, the increase in minor melting peaks as shown in curve 6 continues after the 5 wt% polyethylene blend, despite the decrease in slope. Thus, large amounts of polyethylene up to 10% by weight can be used, but as indicated by the increase in haze rate shown in Table I, limiting the polyethylene content to 5% by weight or to 4% by weight. Can prevent further deterioration of transparency of the product. Dashed lines 7 and 8 in FIG. 2 show the slope of the curve defined by the original minor melting peak of syndiotactic polypropylene alone and the peaks as observed at 2 and 5 wt%, respectively. In both cases, these slopes are substantially greater than the slope of curve 4, which is relatively flat.

  This syndiotactic polypropylene-polyethylene wax mixture can be used in accordance with the present invention to produce any suitable product. Thus, the present invention can be practiced to produce fibers, single or multilayer films, and molded products by either blow molding or compression molding methods. In each case, the polyethylene-syndiotactic polypropylene composition can be heated to a temperature above the major melting peak to produce a molten or plastic body of the composition and further processed into the desired shape. Next, the preform thus produced is cooled to a temperature below the recrystallization temperature to obtain a desired product. This product can be further processed in a manner known to those skilled in the art to obtain the desired product.

  The present invention is particularly applicable to the production of polypropylene films and fibers. A suitable procedure for the production of fibers molded from the polyethylene wax-syndiotactic polypropylene composition of the present invention is disclosed in US Pat. No. 6,416,699 to Gowner. As disclosed in the Golder patent, the syndiotactic polypropylene formulation is heated to a molten state, in this case to a molten state that exceeds the major melting temperature peak, and then extruded to form a fiber preform and quench. Spin in a column and then stretch at any suitable stretch ratio, usually within a range of 2-3.

When the present invention is used in the production of polypropylene film, the molten body is reheated to a temperature above the major melting point peak, extruded through a slot die configuration, and then, for example, US Pat. No. 6,641, to Hanyu et al. It is processed by a suitable tenter frame method as disclosed in No.913. The polyethylene wax-syndiotactic polypropylene blends of the present invention can be used to form a single layer film, but are typically used in multilayer films where a polyethylene-wax syndiotactic polypropylene film can be used to form a surface layer. The For further description of the application of the present invention in the manufacture of fiber and film products, see the aforementioned US Pat. No. 6,416,699 to Golden and No. to Hanyu et al., Which are incorporated herein by reference. See 6,641,993.

  The polyethylene wax syndiotactic polypropylene blends of the present invention can also be used in various molding operations that can take the form of a blow molding operation or a compression molding operation. In blow molding, a plastic polyethylene-syndiotactic polypropylene composition is extruded from a suitable feed structure into a suitably shaped mold cavity with the concomitant supply of air or other gas to form a plastic syndiotactic. A tic polypropylene blend is formed into the desired shape within the mold structure. Using blow molding, a bottle as disclosed in US Pat. No. 6,433,103 to Gunther et al. Or an automobile as disclosed in US Pat. No. 6,294,235 to Detoumay et al. Hollow products of any suitable shape such as fuel tanks can be manufactured. For a further description of blow molding processes that can be used in the practice of the present invention, see the aforementioned US Pat. No. 6,294,235 to Detomay and Gunther et al., Which are incorporated herein by reference. See 6,433,103. In the production of a molded product by compression molding, the shape of the product is formed by the shape of a mold without incidentally introducing a pressurized gas.

  While specific embodiments of the present invention have been described, it will be understood that these modifications may be suggested to one of ordinary skill in the art, and all such modifications are intended to be within the scope of the appended claims. It is intended to cover.

Claims (18)

(A) a large amount of syndiotactic polypropylene having a designated recrystallization temperature and an original minor and original major melting peak;
(B) a small amount of polyethylene wax admixed with the syndiotactic polypropylene, wherein the amount of polyethylene wax is higher than the recrystallization temperature of the admixture above the specified recrystallization peak of the syndiotactic polypropylene; A sufficient amount to give a minor melting peak and a major melting peak, which is a temperature difference that is smaller than the temperature difference between the minor melting peak and the original major melting peak of
Processable polypropylene composition comprising a mixture of   The polyethylene wax is present in the formulation in an amount that results in an increase in the recrystallization temperature of the formulation that is at least 5% greater than the recrystallization temperature of the syndiotactic polypropylene without the addition of the polyethylene wax; The composition of claim 1.   The temperature difference between the major and minor melting peaks of the formulation incorporating the polyethylene wax is at least 1 ° C. higher than the temperature difference between the original major and minor melting peaks without the addition of the polyethylene wax. The composition of claim 1, wherein the composition is decreased in increments of   The composition of claim 1, wherein the polyethylene wax has a molecular weight less than the molecular weight of the syndiotactic polypropylene.   The composition of claim 4, wherein the polyethylene wax has a molecular weight of 5,000 or less.   The temperature difference between the minor melting peak and the major melting peak of the composition incorporating the polyethylene wax is at least 2 greater than the temperature difference between the original minor melting peak and the major melting peak when the polyethylene wax is not added. 6. A composition according to claim 5, wherein the composition decreases in increments of degrees Celsius.   The composition of claim 1, wherein the syndiotactic polypropylene has a syndiotacticity of at least 70% as measured by the percent racemic pentad of the syndiotactic polypropylene.   The slope of the curve defined by the original minor melting peak of the syndiotactic polypropylene and the minor melting peak of the blend of polyethylene wax and the syndiotactic polypropylene is the original major melting of the syndiotactic polypropylene. The composition of claim 1, wherein the composition is greater than a slope of a curve defined by a peak and a major melting peak of the blend of polyethylene wax and the syndiotactic polypropylene.   The temperature difference between the recrystallization temperature of the mixture and the minor melting peak of the mixture is reduced in at least 1 ° C increments than the difference between the original recrystallization temperature and the original minor melting peak. The composition according to claim 1.   The composition of claim 1, wherein the polyethylene wax is present in the blend in an amount of at least 1% by weight. (A) (i) the specified recrystallization temperature and the original minor melting peak and the original second
A large amount of syndiotactic polypropylene with a major melting peak of
(Ii) a small amount of polyethylene wax admixed with the syndiotactic polypropylene, wherein the amount of polyethylene wax depends on the recrystallization temperature of the admixture above the designated recrystallization peak of the syndiotactic polypropylene, A sufficient amount to give a minor melting peak and a major melting peak, which is a temperature difference that is smaller than the temperature difference between the minor melting peak and the original major melting peak of
Providing an ethylene-polypropylene composition comprising:
(B) heating the polyethylene-polypropylene composition to a temperature above the major melting peak of the composition, resulting in a plastic body of the polyethylene-polypropylene composition;
(C) processing the plastic object into the desired shape of the product;
(D) A method of producing a polypropylene product comprising cooling the plastic body to a temperature below the recrystallization temperature of the blend to provide the product.   12. The plastic body is processed by extruding the plastic body from a slot die system to obtain a polypropylene film preform and cooling to a temperature below the crystallization temperature to produce a film. the method of.   The method of claim 11, wherein the plastic body is introduced into a mold and the plastic body is cooled to a temperature below a recrystallization temperature to produce a molded product.   The method of claim 11, wherein the plastic body is extruded from a fiber die system to produce long fibers and cooled to a temperature below the recrystallization temperature of the plastic body to form a fiber product.   The polyethylene wax is present in the formulation in an amount that results in an increase in the recrystallization temperature of the formulation that is at least 5% greater than the specified recrystallization temperature of the syndiotactic polypropylene without the addition of the polyethylene wax. 12. A method according to claim 11 present.   The temperature difference between the major major and minor melting peaks of the formulation incorporating the polyethylene wax is at least 2 greater than the temperature difference between the original major and minor melting peaks without the addition of the polyethylene wax. 12. The method of claim 11, wherein the method is decreased in increments of degrees Celsius.   The slope of the curve defined by the original minor melting peak of the syndiotactic polypropylene and the minor melting peak of the blend of polyethylene wax and the syndiotactic polypropylene is the original major melting of the syndiotactic polypropylene. The method of claim 11, wherein the method is greater than a slope of a curve defined by a peak and a major melting peak of the blend of polyethylene wax and the syndiotactic polypropylene.   The temperature difference between the recrystallization temperature of the mixture and the minor melting peak of the mixture decreased in increments of at least 1 ° C. than the difference between the original crystallization temperature and the original minor melting peak; The method of claim 11.

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